A type of ultrasonic probe capable of three-dimensional imaging is called a three-dimensional mechanical probe. The three-dimensional mechanical probe usually includes a transducer unit configured to emit ultrasonic waves and receive ultrasonic echoes and a stepper motor used as a driver. The controlled stepper motor drives the transducer unit to swing within a predetermined angle range. The transducer unit emits the ultrasonic waves and receives echoes containing human body tissue information at each swing angle to image the human body tissue at each swing angle of the predetermined angle range, thus a three-dimensional image of the human body tissue is formed.
A three-dimensional mechanical probe can be classified as a three-dimensional body surface mechanical probe and a three-dimensional intracavitary mechanical probe. The three-dimensional intracavitary mechanical probe can be driven via a cable, a cord, or other tension member and/or a bevel gear. The bevel gear transmission demands strict use of a material, a machining, and an assembly. Since the three-dimensional intracavitary mechanical probe requires a small size, such as 25 millimeters diameter for the portion to be inserted into human body, and has a complicated interior structure, it is very difficult to machine and assemble a bevel gear transmission in the three-dimensional intracavitary mechanical probe.
A tension transmission device usually includes two cables fixed to one position on a driving shaft. Thus, a transmission between the driving shaft and a driven shaft can be a linear transmission when the driving shaft rotates within a range of plus or minus 90 degrees. However, an included angle θ is defined between the cables and a vertical direction when the driving shaft rotates beyond the range of plus or minus 90 degrees, and the included angle θ increases when the driving shaft continues to rotate outside the range of plus or minus of 90 degrees, thus the tension transmission between the driving shaft and the driven shaft becomes non-linear, which makes it difficult to manipulate the three-dimensional intracavitary mechanical probe.